You are close. Cut the input shaft & the coller that the TO brg. rides on to match the old trans. While you have the coller off take the new clutch disc & slide it on the shaft till it stops. Mark it. Pull the disc off & grind the grooves with a die grinder or Dremel tool till the disc will slide on about 3/8 to 1/2 in. further then originally. Run a half in. drill bit through the mounting holes in the trans. Use 2 allen head bolts 1/2 x 1 1/2 coarse thread for the upper mounting bolts. get bolts & nuts for the lower. Get a driveshaft yoke from the S-10 or practically any 68 up GM & have the drive shaft shortened to fit using the later model yoke. Some guys run them without a crossmember under them but I certainly wouldn,t do it with that long aluminum case.